Sand casting mold production system and sand casting mold production method for producing sand casting mold

ABSTRACT

A sand casting mold production system provided with a nozzle movement device and a control device for the same. The control device is provided with a sand feed position defining part virtually dividing an open region of a top surface part of a frame into a plurality of sub regions and defining coordinates of the individual sub region as sand feed positions on the coordinate system of the nozzle movement device, a height measuring part measuring the height of an internal space of the frame at the individual sand feed positions, and a sand feed determining part using the heights at the individual sand feed positions as the basis to determine the amounts of sand to be fed at the individual sand feed positions. Further, the determined amount of sand is fed to each sand feed position from the sand feed nozzle to the inside of the frame.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sand casting mold production system and sand casting mold production method for filling sand into a frame in which a pattern is placed so as to produce a sand casting mold. In particular, the present invention relates to a sand casting mold production system and sand casting mold production method making a nozzle for feeding sand into the frame move so as to produce a sand casting mold.

2. Description of the Related Art

When producing a sand casting mold, a pattern having the same shape as the product is fabricated, this pattern is placed inside a frame, and sand is filled around the pattern in the frame. The degree of compacting of the sand inside the frame has a great effect on the dimensional precision of the sand casting mold, and therefore it is necessary to suitably fill sand around the pattern inside the frame. For this reason, various devices for suitably feeding and compacting sand inside a frame have been proposed. As one example there is the casting mold production apparatus disclosed in International Publication No. WO2011/142049.

The casting mold production apparatus disclosed in International Publication No. WO2011/142049 is provided with a tank holding sand to be fed to a frame member in which a pattern is placed and a nozzle provided integrally with a bottom end of the tank and feeding sand in the tank to the frame member. This casting mold production apparatus is further provided with a mechanism for compacting the sand fed to the frame member from above and a mechanism for removing sand stuck in the nozzle by air after compacting the sand so as to suppress manufacturing defects in the casting molds.

In general, when producing a casting mold for mass producing large sized products, the pattern and the frame in which the pattern is placed also become large in size. If feeding sand to the inside of a large size frame, the sand easily spreads horizontally and follows the shape of the pattern to penetrate to the bottom side of the pattern. As a result, the height of the sand fed into the frame no longer becomes constant and even. If, in the state where the height of the sand in the frame is not even, compacting the sand from above like with the casting mold production apparatus disclosed in International Publication No. WO2011/142049, the produced casting becomes uneven in compacting of sand in the mold and the problem arises of a drop in dimension precision of the casting.

The casting mold production apparatus disclosed in International Publication No. WO2011/142049 is for producing casting molds for mass production of relatively small products. Therefore, International Publication No. WO2011/142049 discloses nothing about the above problem.

To avoid the above problem, in the past, a worker would visually check the state of the sand filled inside the frame while the worker operated the nozzle of the sand feed device so that the height of the sand would become even.

However, in a large size frame, it is extremely difficult to judge in what kind of order and in what kind of amount sand should be filled at various locations of the frame so that the height of the sand will become constant and even. This is because while sand is being fed to the inside of the frame, the behavior of the sand will change minutely in accordance with the shape of the pattern and the state of the sand. That is, under current conditions, it is difficult to replace human workers with robots for feeding sand into large size frames.

SUMMARY OF THE INVENTION

The present invention provides a casting mold production system which can feed sand into a frame so that the height of the sand becomes constant and even.

According to a first aspect of the present invention, there is provided a sand casting mold production system filling sand in a frame in which a pattern is arranged, the sand casting mold production system comprising:

a sand feed nozzle feeding the sand into the frame;

a nozzle movement device which is configured to make the sand feed nozzle move; and

a control device controlling the nozzle movement device,

wherein the frame is a hollow member having an open top surface part and positioned in a coordinate system of the nozzle movement device,

the control device comprises

a sand feed position defining part virtually dividing an open region of the top surface part of the frame into a plurality of sub regions and defining coordinates of the individual sub regions as sand feed positions on the coordinate system of the nozzle movement device,

a height measuring part measuring a height of an internal space of the frame at the individual sand feed positions, and

a sand feed determining part determining an amount of sand to feed at the individual sand feed positions based on the height at the individual sand feed positions, and

the control device makes the nozzle movement device operate so as to successively position the sand feed nozzle at the individual sand feed positions and feeds the amount of sand determined by the sand feed determining part to each sand feed position from the sand feed nozzle to the inside of the frame.

According to a second aspect of the present invention, there is provided the sand casting mold production system of the first aspect wherein the control device

feeds the determined amount of sand from the sand feed nozzle to the inside of the frame to each sand feed position, then remeasures the height of the internal space of the frame at the individual sand feed positions by the use of the height measuring part,

determines the amount of sand to be fed for any sand feed position where the remeasured height is a predetermined threshold value or more based on the remeasured height, by the use of the sand feed determining part, and

makes the nozzle movement device operate so as to successively place the sand feed nozzle at the sand feed positions where the remeasured height is the predetermined threshold value or more and feeds the amount of sand determined based on the remeasured height from the sand feed nozzle to the inside of the frame.

According to a third aspect of the present invention, there is provided the sand casting mold production system of the first aspect or the second aspect wherein the sand feed position defining part virtually divides the open region into a plurality of sub regions regularly arranged based on any point on the frame, the any point being linked with the coordinate system of the nozzle movement device.

According to a fourth aspect of the present invention, there is provided the sand casting mold production system of any of the first aspect to the third aspect wherein the height measuring part has a 3D visual sensor arranged above the frame, and the 3D visual sensor is used to measure the height of the internal space of the frame at the individual sand feed positions.

According to a fifth aspect of the present invention, there is provided the sand casting mold production system of any of the first aspect to the fourth aspect wherein the nozzle movement device is a robot.

According to a sixth aspect of the present invention, there is provided a sand casting mold production method filling sand in a frame in which a pattern is arranged so as to produce a sand casting mold, comprising:

providing a nozzle movement device making a sand feed nozzle move;

fabricating the frame as a hollow member having an open top surface part and positioning it in a coordinate system of the nozzle movement device;

virtually dividing an open region of the top surface part of the frame into a plurality of sub regions and defining coordinates of the individual sub regions as sand feed positions on the coordinate system of the nozzle movement device;

measuring a height of an internal space of the frame at the individual sand feed positions;

determining an amount of sand to feed at the individual sand feed positions based on the height at the individual sand feed positions; and

making the nozzle movement device operate so as to successively position the sand feed nozzle at the individual sand feed positions and feeding the amount of sand determined for each sand feed position from the sand feed nozzle to the inside of the frame.

According to a seventh aspect of the present invention, there is provided the sand casting mold production method according to the sixth aspect further comprising:

feeding the determined amount of sand from the sand feed nozzle to the inside of the frame to each sand feed position, then remeasuring the height of the internal space of the frame at the individual sand feed positions,

determining the amount of sand to be fed for any sand feed position where the remeasured height is a predetermined threshold value or more based on the remeasured height, and

making the nozzle movement device operate so as to successively place the sand feed nozzle at the sand feed positions where the remeasured height is the predetermined threshold value or more and feeding the amount of sand determined based on the remeasured height from the sand feed nozzle to the inside of the frame.

According to an eighth aspect of the present invention, there is provided the sand casting mold production method according to the sixth aspect or the seventh aspect wherein the virtually divided plurality of sub regions are regularly arranged based on any point on the frame, and the any point is linked with the coordinate system of the nozzle movement device.

According to a ninth aspect of the present invention, there is provided the sand casting mold production method according to any one of the sixth aspect to the eighth aspect further comprising using a 3D visual sensor arranged above the frame when measuring the height of the internal space of the frame at the individual sand feed positions.

According to a 10th aspect of the present invention, there is provided the sand casting mold production method according to any one of the sixth aspect to the ninth aspect the present invention wherein the nozzle movement device is a robot.

These objects, features, and advantages of the present invention and other objects features and advantages will become further clearer from the detailed description of representative embodiments of the present invention shown in the attached drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing the configuration of a sand casting mold production system of one embodiment.

FIG. 2 is a view showing by broken lines a plurality of sub regions into which a region of an open part of a frame shown in FIG. 1 is virtually divided.

FIG. 3 is a flow chart showing the operation of the sand casting mold production system of one embodiment.

FIG. 4A is a cross-sectional schematic view showing a state of a first step in a method of producing a sand casting mold by the sand casting mold production system of one embodiment.

FIG. 4B is a cross-sectional schematic view showing a state of a second step in a method of producing a sand casting mold by the sand casting mold production system of one embodiment.

FIG. 4C is a cross-sectional schematic view showing a state of a third step in a method of producing a sand casting mold by the sand casting mold production system of one embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Next, embodiments of the present invention will be explained with reference to the drawings. In the following drawings, similar members are assigned similar reference notations. To facilitate understanding, these drawings are suitably changed in scale. Further, the embodiments of the sand casting mold production system shown in the drawings are only examples. The sand casting mold production system of the present invention is not limited to the illustrated embodiments.

FIG. 1 is a block diagram showing the configuration of a sand casting mold production system of one embodiment of the present invention.

The sand casting mold production system 1 of the type shown in FIG. 1 comprises a frame 3 inside of which a pattern 2 is placed and a sand feed device 4 feeding sand to the inside of the frame 3.

The sand feed device 4 is provided with a sand feed nozzle 4 a. The pattern 2 has the same shape as the produced product. The frame 3 is fabricated from a hollow member having an open top surface part and is positioned at a predetermined position. Note that the illustrated frame 3 is formed as a hollow box with an open top surface part, but the present invention is not limited to the illustrated shape of frame.

Furthermore, the sand casting mold production system 1, as shown in FIG. 1, comprises a robot 5, a control device controlling the sand feed device 4 and robot 5, and a height measurement sensor 7 measuring the height of the frame 3 or the height of the pattern 2 or sand present inside the frame 3.

The robot 5 is a vertical multiarticulated manipulator. The position at which the frame 3 is fastened is linked with the coordinate system of the robot 5. The tip end of the arm of the robot 5, as shown in FIG. 1, is provided with a hand part 5 a which can freely grip the sand feed nozzle 4 a. The sand feed nozzle 4 a is connected through an elastic tube 4 b to the sand feed device 4. Due to this, just the sand feed nozzle 4 a can be moved by the robot 5. In the present embodiment, a configuration where the hand part 5 a is used to grip the sand feed nozzle 4 a at the tip end of the arm of the robot 5 is employed. However, the present invention is not limited to this configuration. The sand feed nozzle 4 a may also be directly attached to the tip end of the arm of the robot 5.

The height measurement sensor 7, as shown in FIG. 1, is set above the open part 3 a of the frame 3. Further, the height measurement sensor 7 measures the vertical direction distance, that is, the height, from the position of the sensor to the pattern 2 or sand in the frame 3. At a part inside the frame 3 with no pattern 2 or sand, the height measurement sensor 7 measures the height from the position of the sensor to the bottom surface of the frame 3. As the height measurement sensor 7 for measuring such height, a 3D visual sensor is used.

The 3D visual sensor is preferably one which uses the optical sectioning method and binocular stereo system together. Specifically, a projector and video camera are set above the measured object, and the positional relationship between the imaging surface of the video camera and the light emitting part of the projector is determined in advance. If firing a slit of light from the projector to the measured object, a band of light of a higher brightness than the surroundings is formed on the surface of the measured object. This band of light is projected on the imaging surface of the video camera. Further, the position information of the light band projected on the imaging surface of the video camera, for example, on the CCD, is used to measure the distance between the sensor and measured object utilizing the principle of triangulation (optical sectioning method). Furthermore, in such an optical sectioning method, a plurality of bands of light are fired at the entire region of the measured object by a predetermined pitch to measure the measured object as a whole three-dimensionally. Further, to secure measurement precision, it is preferable to jointly use the method of setting two video cameras at the left and right of the projector and capturing images of the measured object by the two video cameras from different directions to measure the measured object three-dimensionally (binocular stereo system) together with the optical sectioning method.

Of course, the invention is not limited to a 3D visual sensor utilizing the above-mentioned optical sectioning method and binocular stereo method, the invention may utilize another 3D measurement method. For example, the method of: measuring the time required from when firing light from a light emitting part to the measured object as a whole to when the reflected light reflected by the measured object reaches the imaging surface of the video camera; and calculating the distance between the sensor and the measured object from the relationship of the measured time and speed of light, that is, the so-called TOF (time of flight) system, may also be utilized.

Furthermore, the control device 6 will be explained.

As shown in FIG. 1, the control device 6 is connected to the sand feed device 4 and robot 5. The control device 6 is a digital computer. Furthermore, the control device 6 comprises a sand feed position defining part 11, robot control part 12, height measuring part 13, and sand feed determining part 14. Below, the different component elements of the control device 6 will be explained in sequence.

The sand feed position defining part 11 virtually divides the region of the open part 3 a of the frame 3 into a plurality of sub regions, defines the individual sub regions as sand feed positions, and outputs these sand feed positions to the robot control part 12. The method of defining sand feed positions will be explained later.

The robot control part 12 makes the robot 5 operate so as to use the hand part 5 a to grip the sand feed nozzle 4 a. Furthermore, the robot control part 12 makes the robot 5 operate so as to place the sand feed nozzle 4 a at the individual sand feed positions defined by the sand feed position defining part 11.

The height measuring part 13 measures the height of the internal space of the frame 3 at the individual sand feed positions. In other words, the height measuring part 13 uses the height measurement sensor 7 to measure the height from the position of the top end part of the frame 3 such as shown in FIG. 1 to the pattern 2 or sand at the inside of the frame 3. At apart inside the frame 3 with no pattern 2 or sand, the height measuring part 17 measures the height from the position of the top end of the frame 3 to the bottom surface of the frame 3.

Specifically, by using the above-mentioned 3D visual sensor as a height measurement sensor 7, the height from the position of the 3D visual sensor to the top end part of the frame 3 is acquired. Furthermore, the height from the position of the 3D visual sensor to the pattern 2 or sand at the individual sand feed positions in the frame 3 is also acquired. On the basis of the difference of such two heights, the height from the position of the top end part of the frame 3 to the pattern 2 or sand at the individual sand feed positions in the frame 3, that is, the height of the internal space of the frame 3, is obtained. The information of the thus measured heights is output to the sand feed determining part 14.

Note that, when using a 3D visual sensor utilizing the above-mentioned optical sectioning method as the height measurement sensor 7, a plurality of slits of light are projected from the 3D visual sensor to the frame 3 as a whole at a predetermined pitch to obtain the 3D shapes of the frame 3 and its inside. In this case, the 3D visual sensor is set so that several slits of light or more cut across the individual sand feed positions of the inside of the frame 3.

The sand feed determining part 14 determines the amount of feed of sand on the basis of the height of the internal space of the frame 3 measured at the individual sand feed positions. If the sand feed nozzle 4 a is placed at a sand feed position in the frame 3, the sand feed device 4 feeds sand into the frame 3 in accordance with the determined amount of feed of sand. Note that the method of determining the amount of feed of sand will be explained later.

Further, the control device 6 including the component elements as mentioned above has an input part 15 connected to the control device 6. The input part 15 has an input device for inputting data relating to the shape and dimensions of the frame 3 to the sand feed position defining part 11. This input device is a push button, a touch panel, keyboard, etc.

Here, the method of defining the sand feed position described above will be illustrated.

FIG. 2 is a view showing by broken lines a plurality of sub regions virtually dividing the region of an open part 3 a when viewing the frame 3 from above. As shown in FIG. 2, the sand feed position defining part 11 virtually divides the region of the open part 3 a of the frame 3 into a plurality of sub regions. Further, the sand feed position defining part 11 defines the coordinates of the sub regions calculated in the following way as sand feed positions.

That is, in the present embodiment, the frame 3 is a hollow box with an open top surface part, and therefore the open region of the open part 3 a when viewing the frame 3 from above is a rectangular region. This rectangular region, as shown in FIG. 2, is virtually divided into a plurality of sub regions of the same area arranged in a matrix of m rows×n columns (in the figure, 19 rows×12 columns).

When equally dividing the region of the open part 3 a of the frame 3 into a plurality of sub regions of m rows×n columns (below, both m and n are natural numbers), if dividing the horizontal dimension of the open part 3 a (in FIG. 2, x-direction dimension) by the value of n and dividing the vertical dimension of the open part 3 a (in FIG. 2, y-direction dimension) by the value of m, the horizontal dimensions and vertical dimensions of the individual sub regions are obtained. In other words, the pitch between sub regions in the horizontal direction and vertical direction is obtained. Note that, the frame 3 is designed in advance corresponding to the pattern 2, and therefore it is easy to determine the horizontal dimension and vertical dimension of the open part 3 a.

Furthermore, when defining the placement surface for setting the frame 3 by 2D coordinates, the horizontal direction of the open part 3 a of the frame 3 is made one coordinate axis (X-axis) on the 2D coordinates, while the vertical direction of the open part 3 a of the frame 3 is made the other coordinate axis (Y-axis) on the 2D coordinates. Further, if making one corner part 3 b at the open part 3 a of the frame 3 a reference point, it is possible to calculate the coordinates of sub regions (center positions of sub regions) present at the m-th row and n-th column from that reference point. That is, when making the corner part 3 b of the open part 3 a the reference point, the X-coordinate value of the center of the sub region is the value obtained by subtracting half of one pitch of the sub regions in the horizontal direction from the value of n times the pitch in the horizontal direction. The Y-coordinate value of the center of the sub region is the value obtained by subtracting half of one pitch of the sub regions in the vertical direction from the value of m times the pitch in the vertical direction. Furthermore, by calibrating in advance the positional relationship between the position of the corner part 3 b of the open part 3 a and the origin of the operation of the robot 5, it is possible to acquire the coordinates of the sub regions with respect to the origin of the operation of the robot 5 by calculation.

Based on the above technique, a program is prepared in advance positioning the frame 3 on the coordinate system of the robot 5 and defining the coordinates of the individual sub regions as sand feed positions on the coordinate system of the robot 5. This program is stored in the sand feed position defining part 11.

That is, if the input part 15 is used to input the horizontal dimension and vertical dimension of the open part 3 a and the number of rows m and number of columns n of the divisions, the sand feed position defining part 11 calculates the coordinates of the individual sub regions with respect to the origin of operation of the robot 5. The coordinates of the sub regions are defined as sand feed positions for feeding sand from the sand feed nozzle 4 a. The sand feed positions are output to the robot control part 12.

Further, the robot control part 12 can use the sand feed positions output from the sand feed position defining part 11 as the basis to make the sand feed nozzle 4 a successively move to the individual sand feed positions by the hand part 5 a of the robot 5.

Regarding the order of movement of the sand feed nozzle 4 a, the sub region positioned at the corner part 3 b of the open part 3 a shown in FIG. 2 is used as the starting point. Further, the sand feed nozzle 4 a is made to move from the sub region at one end in the row direction to the sub region at the other end, then move to the adjoining row, move in the opposite direction to the previous row, and repeat this. If making the sand feed nozzle 4 a move by such an order, the pitch of movement of the nozzle becomes constant, and therefore the robot 4 need not be made to perform a complicated operation. Of course, the control device 6 may make the sand feed nozzle 4 a move by another order of movement. Since the control device 6 acquires the coordinates of the sub regions by the sand feed position defining part 11, the order of making sand feed nozzle 4 a move with respect to the sub regions can be changed to various orders of movement.

Note that, in the present application, the sand feed position defining part 11 need only be one virtually dividing the open region of the top surface part of the frame 3 into a plurality of sub regions regularly arranged with reference to any point on the frame 3. This is because if the plurality of sub regions are arranged with respect to a reference point based on a certain rule, it is possible to easily calculate the coordinates of the sub regions with respect to the reference point from a numerical formula based on that regularity. For this reason, in the present application, the shape of the frame 3 is not limited to the hollow box with the open top surface part such as shown in FIG. 1 and FIG. 2. Various shapes of frames 3 may be used corresponding to the shape of the pattern 2. The plurality of sub regions virtually divided by the sand feed position defining part 11 need only be arranged regularly with respect to any point on the frame 3. Therefore, the shapes of the sub regions are not limited to the square shapes such as shown in FIG. 2.

Method of Production of Casting Mold

Next, the method of production of a casting mold using the above-mentioned sand casting mold production system 1 will be explained. Here, the method of producing a sand casting mold using a frame 3 of a shape such as shown in FIG. 1 and FIG. 2 will be described.

FIG. 3 is a flow chart showing the operation of the sand casting mold production system 1 shown in FIG. 1. FIG. 4A to FIG. 4C are cross-sectional schematic views showing states of different steps in a method of producing a sand casting mold by the sand casting mold production system 1.

As shown in FIG. 3, if the sand casting mold production system 1 is started up, the sand feed position defining part 11 of the control device 6 virtually divides the region of the open part 3 a of the frame 3 into a plurality of sub regions. An example of the form of this division is as shown in FIG. 2. Furthermore, the control device 6 defines coordinates of sub regions with respect to the origin of operation of the robot 5 as sand feed positions, on the basis of the above-mentioned method of definition of sand feed positions (FIG. 3, step S1).

Note that the required number of rows m and number of columns n when setting sub regions such as shown in FIG. 2 and the horizontal dimension and vertical dimension of the open part 3 a are input in advance into the control device 6.

After this, the height measuring part 13 of the control device 6 measures the height of the internal space of the frame 3 corresponding to each defined sand feed position by the use of the height measurement sensor 7 (FIG. 3, step S2). FIG. 4A is a schematic cross-sectional view of the state of step S2 of FIG. 3. As the height measurement sensor 7, the above-mentioned such 3D visual sensor is used. The 3D visual sensor, as shown in FIG. 4A by the broken line arrow, measures the height from the position P at the top end part of the frame 3 to the bottom of the frame 3 at each sand feed position (z-direction distance in figure). Furthermore, the 3D visual sensor, as shown in FIG. 4A by the broken line arrow, measures the height based on the position P at the top end part of the frame 3 to the surface of the pattern 2 at each sand feed position (z-direction distance in figure).

Next, the sand feed determining part 14 of the control device 6 determines the amount of sand to be fed at the individual sand feed positions on the basis of the height of the internal space of the frame 3 measured at the individual sand feed positions (FIG. 3, step S3).

Next, the control device 6 makes the robot 5 operate so as to grip the sand feed nozzle 4 a by the hand part 5 a of the robot 5 and successively place it at the individual defined sand feed positions. At this time, the height coordinates of the individual sand feed positions are made constant. Further, the control device 6 controls the sand feed device 4 so as to feed the amount of sand determined at step S3 from the sand feed nozzle 4 a to the inside of the frame 3 for each sand feed position (FIG. 3, step S4).

FIG. 4B is a schematic cross-sectional view of the states of step S3 to step S4 of FIG. 3. In FIG. 4B, the amounts of feed of sand determined for the individual sand feed positions are shown by bar shaped schematic cross-sections. As shown in FIG. 4B, the control device 6 successively places the sand feed nozzle 4 a at the individual defined sand feed positions. Further, each time the sand feed nozzle 4 a is placed at an individual sand feed position, the determined amount of sand is fed from the sand feed nozzle 4 a to the inside of the frame 3.

The sand feed device 4 is configured so that when the sand feed nozzle 4 a feeds sand to the inside of the frame 3, a certain amount of sand per unit time is discharged from the sand feed nozzle 4 a and adjusts the time for discharging sand from the sand feed nozzle 4 a.

Note that, the amount of feed of sand determined at step S3 is calculated by the following method. As explained above, the horizontal and vertical dimensions of the open part 3 a of the frame 3 and the number of rows m and number of columns n for showing the sub regions are known values. For this reason, it is possible to calculate the horizontal and vertical dimensions of the individual sub regions and due to this also possible to calculate the areas of the individual sub regions. Further, using the product of the calculated areas of the individual sub regions and the height of the internal space of the frame 3 measured for the individual sand feed positions, it is possible to calculate the volume of the space. Further, the amount of feed of sand is not the same as the calculated volume. It is that volume multiplied with a predetermined ratio. The reason is that sand may not remain at the fed location, but may flow to the surroundings, and therefore, if the amount of feed of sand is made the same as the volume calculated in the above way, the sand is liable to overflow from the frame 3.

Next, as explained above, when a single sand feed operation is finished for all defined sand feed positions, the control device 6 makes the sand feed nozzle 4 a stand by outside of the measurement area of the height measurement sensor 7. Further, the control device 6 again measures the height of the internal space of the frame 3 at the individual sand feed positions by the use of the height measurement sensor 7 (FIG. 3, step S5).

FIG. 4C is a schematic cross-sectional view showing the state of step S5 of FIG. 3. In FIG. 4C, the state is shown when at all defined sand feed positions, the determined amount of sand is actually fed inside the frame 3. Even if sand is fed according to step S4, the sand sometimes spreads horizontally and follows the shape of the pattern 2 to penetrate to the inside of the pattern. In this case, as shown in FIG. 4C, a recess is formed at the top surface of the sand 16 fed to the inside of the frame 3. For this reason, the height measurement sensor 7 is again used to measure the height of the internal space of the frame 3 at the individual sand feed positions.

Next, the control device 6 compares the height of the internal space of the frame 3 at different sand feed positions measured at step S5 with a predetermined threshold value (FIG. 3, step S6). If, as a result, the measured heights at all of the sand feed positions are smaller than the predetermined threshold value, the control device 6 judges that no recessed part such as shown in FIG. 4C has occurred at any of the sand feed positions and ends the sand feed operation.

On the other hand, if, at the above step S6, the measured height at any of the sand feed positions is the same as a predetermined threshold value or larger than the same, a recessed part such as shown in FIG. 4C is formed. For this reason, the control device 6 determines the amount of sand to be again fed to the individual sand feed positions judged at the above step S6 to have a predetermined threshold value or more of height (FIG. 3, step S7).

The amount of sand feed at the above step S7 is determined by the same method as the method for determining the amount of sand feed at step S3. That is, the product of the areas of the individual sub regions in the open part 3 a of the frame 3 and the height of the internal space of the frame 3 measured for the individual sand feed positions at step S5 is used to calculate the volume of the space. Further, the volume multiplied with a predetermined ratio is made the sand feed amount.

Furthermore, the control device 6 makes the robot 5 operate so as to successively place the sand feed nozzle 4 a at the individual sand feed positions judged to have a predetermined threshold value or more of height as explained above. The position of the sand feed nozzle 4 a in the height direction at the sand feed position is made constant. Further, each time the sand feed nozzle 4 a is placed at a sand feed position judged to have a predetermined threshold value or more of height, the control device 6 controls the sand feed device 4 so as to feed the amount of sand determined at step S7 to the inside of the frame 3 (FIG. 3, step S8).

The process of the above-mentioned step S5 to step S8 is performed at least once after step S4. In particular, in the present embodiment, the process of step S5 to step S8 is repeated until the measured heights at all of the sand feed positions become smaller than the predetermined threshold value. Due to this, there is no longer any recessed part of sand 16 such as shown in FIG. 4C and the height of the sand in the frame 3 becomes constant and even.

According to the sand casting mold production system 1 of the present embodiment explained above, the region of the open part 3 a of the frame 3 is virtually divided into a plurality of sub regions and the coordinates of the individual sub regions are defined as sand feed positions on the coordinate system of the robot 5. Due to this, the robot 5 is made to use the hand part 5 a to grip the sand feed nozzle 4 a and make it successively move to the individual sand feed positions. Further, the height of the internal space of the frame 3 at the individual sand feed positions is measured, and the measured heights are used as the basis to determine the amounts of sand to be fed at the individual sand feed positions. Due to this, it is possible to feed the determined amount of sand to each sand feed position from the sand feed nozzle 4 a to the inside of the frame 3. That is, it is possible to automate the previous work of workers operating the sand feed nozzle so that the height of the sand in the frame became even.

Further, according to the present embodiment, the operation of feeding a determined amount of sand to each sand feed position, then measuring the height of the internal space of the frame 3 at the individual sand feed positions and determining the amount of sand feed based on the heights is repeated a plurality of times. In this operation, only sand feed positions with measured heights being a predetermined threshold value or more are fed with amounts of sand based on the measured heights. For this reason, even if the condition of the sand filled inside the frame finely changes, a suitable amount of sand can be filled inside the frame so that the height of the sand becomes constant and even. As a result, the compacting of the sand of the produced casting mold becomes even and casting molds with good dimensional precision can be produced. In particular, as shown in FIG. 1, when the bottom part of the pattern 2 is narrowed or the frame 3 is large in size, the sand casting mold production system 1 of the present embodiment enables sand to be fed to the inside of a frame 3 so that the height of the sand becomes constant and even. Furthermore, the minimum necessary amount of sand can be accurately fed to a location to be refilled with sand. Further, sand will never overflow from the frame during the sand feed operation.

Further, according to the present embodiment, the height measurement sensor 7 is placed above the frame 3, so movement of the sand feed nozzle 4 a is not hindered by the height measurement sensor 7. By using a 3D visual sensor as the height measurement sensor 7, it is possible to easily measure the height of the internal space of the frame 3 at the individual sand feed positions.

Note that, in this application, a “frame” means a casting frame when the casting mold produced is equipped with a casting frame or the mold frame when there is no casting frame. Further, the casting mold produced includes the case of being equipped with casting frames and the case of no casting frames where the sand is shaped inside the frame, then is taken out from the frame.

Above, the present invention was explained with reference to the example of a robot 5 as the nozzle movement device for making the sand feed nozzle 4 a move, but the nozzle movement device of the present invention is not limited to a robot. Further, the robot is also not limited to a vertical multiarticulated manipulator.

Advantageous Effects of Invention

According to the first aspect and sixth aspect of the present invention, when producing a casting mold, a nozzle movement device is used to make a sand feed nozzle successively move to individual sand feed positions virtually dividing an open region of a frame. Further, the heights of the internal space of the frame measured at the individual sand feed positions are used as the basis to determine the amounts of sand to be fed at the individual sand feed positions. Due to this, it is possible to feed the determined amount of sand to each sand feed position from the sand feed nozzle to the inside of the frame. That is, according to the present invention, it is possible to automate the previous work of workers operating the sand feed nozzle so that the height of the sand in the frame became even.

Further, according to the second aspect and seventh aspect of the present invention, the operation of feeding a determined amount of sand to each sand feed position, then measuring the height of the internal space of the frame at each sand feed position is repeated a plurality of times. Further, only sand feed positions with measured heights being a predetermined threshold value or more are fed with amounts of sand based on the measured heights. For this reason, even if the condition of the sand fed to the inside of the frame finely changes, a suitable amount of sand can be filled inside of the frame so that the height of the sand becomes constant and even. As a result, the compacting of the sand of the produced casting mold becomes even and casting molds with good dimensional precision can be produced. In particular, when the bottom part of the pattern is narrowed or when the frame is large in size, the sand casting mold production system of the present invention can be used to feed sand to the inside of the frame so that the height of the sand becomes constant and even.

According to the third aspect and eighth aspect of the present invention, the virtually divided plurality of sub regions are a plurality of sub regions regularly arranged with reference to any point on the frame. If in this way a plurality of sub regions are arranged with respect to a reference point based on a certain rule, it is possible to easily calculate and define the coordinates of the sub regions with respect to the reference point from a numerical formula based on that regularity.

According to the fourth aspect and ninth aspect of the present invention, the 3D visual sensor arranged above the frame can easily measure the height of the internal space at the individual sand feed positions. Further, the 3D visual sensor is arranged above the frame, and therefore movement of the sand feed nozzle is not inhibited by the 3D visual sensor.

According to the fifth aspect and 10th aspect of the present invention, a robot can be used as the nozzle movement device so as easily and accurately move the sand feed nozzle.

Above, typical embodiments were shown, but the present invention is not limited to the above embodiments. The above embodiments may be changed to various shapes, structures, materials, etc. within a scope not exceeding the concept of the present invention. 

What is claimed is:
 1. A sand casting mold production system filling sand in a frame in which a pattern is arranged so as to produce a sand casting mold, said sand casting mold production system comprising: a sand feed nozzle feeding said sand into said frame; a nozzle movement device which is configured to make said sand feed nozzle move; and a control device controlling said nozzle movement device, wherein said frame is a hollow member having an open top surface part and positioned in a coordinate system of said nozzle movement device, said control device comprises a sand feed position defining part virtually dividing an open region of said top surface part of said frame into a plurality of sub regions and defining coordinates of said individual sub regions as sand feed positions on the coordinate system of said nozzle movement device, a height measuring part measuring a height of an internal space of said frame at the individual sand feed positions, and a sand feed determining part determining an amount of sand to feed at said individual sand feed positions based on said height at said individual sand feed positions, and said control device makes said nozzle movement device operate so as to successively position said sand feed nozzle at the individual sand feed positions and feeds the amount of sand determined by said sand feed determining part to each said sand feed position from said sand feed nozzle to the inside of said frame.
 2. The sand casting mold production system according to claim 1, wherein said control device feeds said determined amount of sand from said sand feed nozzle to the inside of said frame to each said sand feed position, then remeasures the height of the internal space of said frame at said individual sand feed positions by the use of said height measuring part, determines the amount of sand to be fed for any sand feed position where the remeasured height is a predetermined threshold value or more based on said remeasured height, by the use of said sand feed determining part, and makes said nozzle movement device operate so as to successively place said sand feed nozzle at said sand feed positions where said remeasured height is said predetermined threshold value or more and feeding the amount of sand determined based on said remeasured height from said sand feed nozzle to the inside of said frame.
 3. The sand casting mold production system according to claim 1, wherein said sand feed position defining part virtually divides said open region into said plurality of sub regions regularly arranged based on any point on said frame, said any point being linked with the coordinate system of said nozzle movement device.
 4. The sand casting mold production system according to claim 1, wherein said height measuring part has a 3D visual sensor arranged above said frame, and said 3D visual sensor is used to measure the height of the internal space of said frame at said individual sand feed positions.
 5. The sand casting mold production system according to claim 1, wherein said nozzle movement device is a robot.
 6. A sand casting mold production method filling sand in a frame in which a pattern is arranged so as to produce a sand casting mold, comprising: providing a nozzle movement device making a sand feed nozzle move; fabricating said frame as a hollow member having an open top surface part and positioning it in a coordinate system of said nozzle movement device; virtually dividing an open region of said top surface part of said frame into a plurality of sub regions and defining coordinates of said individual sub regions as sand feed positions on the coordinate system of said nozzle movement device; measuring a height of an internal space of said frame at said individual sand feed positions; determining an amount of sand to feed at said individual sand feed positions based on said height at said individual sand feed positions; and making said nozzle movement device operate so as to successively position said sand feed nozzle at said individual sand feed positions and feeding the amount of sand determined for each said sand feed position from said sand feed nozzle to the inside of said frame.
 7. The sand casting mold production method according to claim 6 further comprising: feeding said determined amount of sand from said sand feed nozzle to the inside of said frame for each said sand feed position, then remeasuring the height of the internal space of said frame at said individual sand feed positions, determining the amount of sand to be fed for any sand feed position where the remeasured height is a predetermined threshold value or more based on said remeasured height, and making said nozzle movement device operate so as to successively place said sand feed nozzle at said sand feed positions where said remeasured height is said predetermined threshold value or more and feeding the amount of sand determined based on said remeasured height from said sand feed nozzle to the inside of said frame.
 8. The sand casting mold production method according to claim 6 wherein said virtually divided plurality of sub regions are regularly arranged based on any point on said frame, and said any point is linked with the coordinate system of said nozzle movement device.
 9. The sand casting mold production method according to claim 6 further comprising using a 3D visual sensor arranged above said frame when measuring the height of the internal space of said frame at said individual sand feed positions.
 10. The sand casting mold production method according to claim 6 wherein said nozzle movement device is a robot. 